Networking among a large number of data stations has found widespread use. A ring bus maybe connected to a number of stations each of which has the capacity to receive from and transmit to the others. A number of prior efforts are described in Champlin et al. U.S. Pat. Nos. 4,665,518 granted May 12, 1987, 4,627,070 granted Dec. 2, 1986 and 4,486,852 granted Dec. 4, 1984; Miller et al. U.S. Pat. No. 4,038,494 granted Jul. 26, 1977 and Niemi et al. U.S. Pat. No. 3,980,820 granted Sep. 14, 1976. Familiarity with the disclosures in these patents will assist in understanding the present invention which constitutes an improvement that allows operation of the data bus at higher speeds without loss of integrity of the transmitted signal.
Prior practice for granting access did not allow immediate access for high priority messages. Existing systems allow one or more additional low priority messages to gain access before a waiting higher priority message can be transmitted.